Pyrometallurgical refining process for copper



United States Patent O 8 Claims. (in. 75-75 The present inventionrelates to a pyrometallurgical refining process for copper.

An object of the present invention is to provide an improved process forrefining copper, which can economically be effected with a high reactionefiiciency.

Another object of the present invention is to provide a new process forrefining copper, wherein the maximum result in the heating, oxidationand reduction can be fully achieved solely through the feeding of fuelblended with air containing oxygen in various densities (hereinafterreferred to as air).

A further object of the present invention is to provide a new processwherein copper can be refined by appropriately adjusting the ratio offuel to air respectively for each stage of heating, oxidation andreduction without the aid of any other additional fuel.

Other objects, features and advantages of the present invention will beapparent from the following description.

The conventional pyrometallurigical process for copper refining includesthe stages of anode refining into refined blister, followed byelectrolytic refining into copper cathode, and subsequent melting andcasting into wire bars. Similar processes are also widely practised inthe treating and refining of copper scrap.

These conventional processes generally comprise melting copper charge,heating in a reverberatory or any other type of suitable furnace, andremoving impurities container in the said charge by oxidation with air,and finally reducing Cu O.

Oxidation is effected by means of air being blown onto the surface ofmolten mass or into the molten mass, causing to separate Pb, Zn, S, As,Sb, Ni, Co, Mn, Bi and Fe contained in the molten mass from the moltencopper. The volatile impurities are carried away in the waste gas,whilst those remaining in the slag floating on the surface of moltencopper are skimmed out of the furnace. The molten copper remaining inthe furnace is fully or almost saturated with Cu O. When the said moltencopper is reduced with a reducing agent to remove oxygen, the refiningof copper will then be completed. The thus-refined copper is then castin casting moulds to the desired form. The reducing operation as hereinset forth is the so-called poling wherein green wood is considered asthe most suitable as a reducing agent. Since the suitability of greenwood referred to above depends on its water content, size and shape, itsavailability and cost offers an economic problem.

In all hitherto known refining processes, since fuels are generallyburnt on the surface of molten mass, a considerable amount of heatdissipates in the course of the oxidation and poling operations.Furthermore, during the reduction of the large amount of Cu O which isformed during oxidation, the reaction between green wood and Cu O iscarried out only on the surface of molten mass, and because ofevaporation of the moisture in the green wood with the progress of time,stirring action in the course of said reaction tends to decrease. Thus,the reducing action takes a long period of time.

In view of the increasing scarcity of the suitable green wood, theabove-mentioned conventional processes are exposed to the difiiculty inensuring economic maintenanoe of heat efiiciency as well as reactionefliciency. The present invention is to provide an improved refiningprocess which entirely overcomes these above-mentioned defects anddisadvantages.

The characteristic feature of the present invention lies in that thebest results can be achieved in each stage of heating, oxidation andreduction by merely feeding fuel blended with air.

The fuel used in the present invention may be liquid fuels such as heavyoil and light oil, or pulverized carbonaceous material including solidfuels such as coal, coke, charcoal, saw-dust and the like.

In general, these fuels, having a wide range of choice, are easily andcheaply available on the market. They are more economical than greenwood normally used.

Of the above-mentioned fuels, these in the powdered form are mixed withair in the desired ratio and blown beneath the surface of the moltenmass, by means of a combined mixing and feeding apparatus such asvariable speed feeder with injector. On the other hand, of the saidfuels, liquid fuels are similarly blown into the molten mass in atomizedform by such means as an injection feeder.

The refining reaction takes place in two stages, namely the oxidationand the reduction of the molten copper. In the oxidation stage,selective oxidation is effected at optimum temperature by utilizing thelower oxidizing tendency of copper than other impurities, while in thereducing stage, deoxidation is carried out at optimum temperature by aclose contact of a reducing agent with oxygen in molten copper, and itis to be noted that optimum temperature is also required in subsequentcasting operation.

After further research and numerous experiments, taking intoconsideration the special features of the refining processes describedabove, it has been determined that better results can be achieved byappropriately regulating the mixing ratio of fuel to air respectively ineach stage of heating, oxidation and reduction. In this case, the oxygenratio, namely the ratio of the actually supplied amount of oxygen (b) tothe theoretical amount of oxygen (a) necessary for combustion, that is,b/aXlOO (percent), within the ranges of approximately to 130% duringheating, within the range of approximately to 200% during oxidation andwithin the range of approximately 20 to 100% during reduction, in orderto effectively accomplish the respective objects.

To summarize, according to the present invention, the desired refiningcan be advantageously and economically carried out by merely adjustingthe above-mentioned oxygen ratio within the rang-e of 20 to 200%,without the aid of the additional or supplemental fuel such as heavyoil, as in the case of conventional known processes. Furthermore,because of its simple and inexpensive operation, the process of thepresent invention is superior to any of the conventional processes.

Moreover, the fuel used in this process may be one or a mixture of twoor more kinds of fuels. Further, a different kind of fuel mayrespectively be used for each stage of oxidation, reduction and heating,or instead thereof, the oxygen density in the air may sometimes bevaried with the kind of fuel used.

In the present invention, since all kinds of fuels, for which the oxygenratio has appropriately been adjusted, are always blown into the bath ofmolten copper, the heat efficiency is remarkably improved. Thus, nosupplemental heating is necessary in the present process due to theimproved heat efliciency, although in the usual processes additional orsupplemental heating fuel is required. Furthermore, in the oxidationstage in the process of the present invention, due to the low partialpresshould respectively be adjusted sure of oxygen in the combustiongas, impurities may etfectively be separated and eliminated to a desiredextent by oxidation without any excessive increase of oxygen in themolten copper. Also in the reduction stage, the reac- Example 2 In amanner similar to that in Example 1, blister copper was refined withpulverized charcoal.

After the first charging of molten copper from contion can rapidly beeffected by a close contact of Cu O 5 in molten copper with reducingmaterial, because violent the g Was treated in the P y Stage forstirring takes place throughout the said stage. In this 25 Inihunder theblowing conditions Where the Char case, the reaction velocity isaccelerated by the regulated e031 feeding rate was kg/Ihihand the Oxygenatio temperature conducive towards chemical reaction with f; and ill thenext Stage for 35 under blowing said temperature maintained by fuelcombustion taking 10 eohdltiehs Where the Charcoal feeding rate wasplace within molten mass. On-the other hand, there is and the Oxygenratio 30 t0 After the a further advantage in that the molten copper ispro Second charging of molten PP from e0hVeIter, the tected fromreoxidation with unburnt carbonaceous matecharge was first treated for45 under eohditlehs i l floating on i f where the charcoal feeding ratewas 0.8 kg./min. and Kinds of copper material to which the presentinventhe y e ratio 140%, and in the next Stage of 35 milk tion areapplicable, include blister copper or electrolytic Under blowingConditions Where the Charcoal feedihg fate copper and/ or scrap copperand the like. Particularly, W35 kgJITll'hthe Oxygen ratio 30 t0 Afterthis process is most effective in anode refining when the Secondcharging of molten PP from Converter, lt copper i li d fr convertel; thecharge was first treated for 45 min. under the con- The above-mentionedfeatures of this invention will ditiohs Where the C031 feeding rate waskgJmmand b apparent f h f ll i examples, the oxygen ratio 140% and inthe next stage for 2 hours Th invention i further d ib d i h foll iunder the conditions where the charcoal feeding rate examples which areillustrative but not limitative thereof. was kg/ Ini11- and the Oxygenratio 30 t0 The charcoal used was as follows. Example 1 Type of charcoalShiro-Zumr (whitlsh charcoal). Approximately 20 metric tons of moltencopper (con- Size 5 mfish taming 0.02% and O 0.0%) from converter were pi t analyses; charged in a 40 metric ton cylindrical anode furnace, andc l ifi value 920 cal/kg slag floated on the surface of molten mass wasskimmed 3 Volatile matter 5% off, and then pulverized coal was blowninto the molten 0 Fixed carbon 4 Copper at the rate of 0.8 kg./min. andthe oxygen ratio Ash maintained at 150%. Moisture 10 7% After min.blowing, a sample of the molten copper S lf (103%. was taken out foranalysis. As the S content was found below 0.01%, the coal feeding ratewas readjusted to 1.4 35 Analyses of original charge and finishedrefined prodkg./min. and the oxygen ratio to 90 to 100%, under uctshowed as follows. which conditions pulverized coal was blown into themolten copper for one hour. P t

Then the blowing was stopped once for receiving anmen other supply ofmolten copper from the converter. Ap- Cu Pb S 0 Others Total proximately20 metric tons of molten copper (containing S 0.02% and O 0.6%)werecharged in the said anode Charge 9M5 018 0.018 M4 bal 100 furnace.After slag being skimmed 01f, pulv-enzed coal Product 99,38 0,14 M04 010bal 100 was blown into the molten copper for 20min. under the conditionswhere the coal feeding rate was 0.8 kg./min. and the oxygen ratio 150%.Example 3 c 0 a fig'g g fi igg i 1& 5 5 5 3352? 23 1; In a mannersimilar to that in Example 1, blister copper conditions the blowing wascontinued for 2.5 hours. A convmter was refined by blowmg mlxture ofportion of molten copper was taken out and analysed verized coal andfine powdered charcoal mto molten cop- Since the result thereof wasfound to be satisfactory, After the first chargmg 9 molten copper fromthe blowing was stopped and the refined copper cast into verter thecharge was fi m the first Stage for 0 moulds. ulfnigr the vtilowirgC(fndltlOlS wahlerell ienfuell feedlfi g rate o e mix ure 0 pu venze coan r e c arcoa in e The pulvenzed coal used was as follows' mixing ratio'by weight of 50:50, was 0.8 kg./min. and the Type of coal Washedpulverized coal. oxygen ratio 140%, and in the next stage of 40 min.under Size -150 mesh. the conditions where the fuel feeding rate was 1.5kg./min. Proximate analyses: and oxygen ratio 30%. After the secondcharging of Calorific value 7,910 cal./ kg. molten copper fromconverter, the charge was treated first Volatile matter 36.5%. for 45min. under the conditions where the fuel feeding Fixed carbon 56.0%.rate was 0.8 kg./min. and oxygen ratio 140% and then for Ash 5.9%. 2.5hours under the conditions where the fuel feeding Moisture 1.6%. ratewas 2.5 kg./ min. and oxygen ratio 30 to 32%. Sulfur 0.4%, Fuels usedWere the same as in Example 1 and Exam- I ple 2 respectively. Analysesof Oflglhal charge and finlshed refined P On the other hand, analyses oforiginal charge and finuct showed as follows: ished refined productshowed as follows.

Percent Percent Cu Pb S 0 Others Total Cu Pb S 0 Others Total Charge98.73 0.13 0. 019 0. e0 bal 100 Charge 98.89 0.16 0.020 0.61 bal 100Product 99.40 0.12 0. 007 0.10 bal 100 Product 99.35 0.15 0. 008 0.10bal 100 Example 4 53 metric tons of electrolytic copper were chargedinto a 5 5 metric ton reverberatory furnace and melted by burning heavyoil. Scum was skimmed out, and then pulverized charcoal was blown intothe molten copper under the conditions where the fuel feeding rate was2.5 kg./min. and the oxygen ratio 30 to 33%. After blowing for 1.5hours, a portion of melt was taken out and analysed. As the result wasjudged as satisfactory, the blowing was stopped and the finished productcast in the usual manner into wire bars.

The pulverized charcoal used was similar to that in Example 2. Analysesof the wire bar obtained were as follows.

Example 5 54 metric tons of electrolytic copper were charged into a 55metric ton reverberatory furnace and melted by burning heavy oil. Scumwas skimmed out. Then, saw-dust was blown into the molten mass under theconditions where the fuel feeding rate was approximately 5 kg./ min. andthe oxygen ratio 27 to 30%. A portion of melt was taken out and analysedafter blowing for 80 min. As the result was found satisfactory, theblowing was stopped and the finished product cast in the usual mannerinto wire bars.

Analysis of the saw-dust used was as follows.

Proximate analyses:

Calorific value ca1./kg. 4,510 Moisture (wet base) percent 30.1 Ash do0.7 Volatile matter do 56.2 Fixed carbon do 43.1

Elementary analyses: Percent S 0.05 H 6.27

Analyses of wire bar obtained were as follows.

Percent Cu 99.97 Fe 0.0005 Ni 0.0003 Pb 0.0008 S 0.0010 Sb 0.0002 As0.0002 Sn 0.0001 0 0.024

Others bal. Total 100 Example 6 Into a 60 metric ton reverberatory anodefurnace, 58 metric tons of blister copper (containing S 0.027% and O0.38%) were charged in a molten state. Then, after skimming 01f slagfloating on the surface of molten copper, light oil was blown into themolten mass, under the conditions where the oil feeding rate was 1liter/min. and the oxygen ratio 140%. After blowing for 45 min., a

Calorific value cal./kg. 11,500 Specific gravity 0.82 Sulfur percent0.20

The analyses of original charge and finished product were as follows:

Percent Cu Pb S 0 Others Total Charge 98. 0. 15 0. 018 0. 68 bal Product99. 34 0. 14 0. 005 0. 10 bal 100 What is claimed is:

1. A pyrometallurgical refining process for copper, wherein a moltenbath of unrefined copper is subjected to consecutive stages of heating,oxidation and reduction, said process comprising the steps of blowingdirectly into the bath of unrefined copper a mixture of oxygen and afuel selected from the group consisting of liquid oil and solidcarbonaceous material while heating the bath, adjusting the volume ofoxygen in the mixture to an oxygen-fuel ratio capable of oxidizing thecopper, continuing the blowing of the adjusted mixture directly into thecopper bath until the oxidation is completed, adjusting the volume ofoxygen in the mixture to an oxygen-fuel ratio capable of reducing thecopper, and then continuing the blowing of the adjusted mixture directlyinto the copper bath until the reduction is completed.

2. A process in accordance with claim 1, wherein the unrefined copper isselected from the group consisting of blister copper, electrolyticcopper and scrap copper.

3. A process in accordance with claim 1, wherein the unrefined copperconsists of a mixture of two different substances selected from thegroup consisting of blister copper, electrolytic copper and scrapcopper.

4. A process in accordance with claim 1, wherein said fuel consists of amixture of liquid oil and solid carbonaceous material.

5. A pyrometallurgical refining process for copper, wherein a moltenbath of unrefined copper is subjected to consecutive stages of heating,oxidation and reduction, said process comprising the steps of blowingdirectly into the bath of unrefined copper a mixture of oxygen and afuel selected from the group consisting of liquid oil and solidcarbonaceous material while heating the bath, the oxygen b/a ratioranging between 80 and 130, adjusting the oxygen b/a ratio to oneranging between 100 and 200, continuing the blowing of the adjustedmixture directly into the copper bath until the oxidation is completed,adjusting the oxygen b/a ratio to one ranging between 20 and 100, andthen continuing the blowing of the adjusted mixture directly into thecopper bath until the reduction is completed, said oxygen b/a ratiobeing one hundred times the ratio of the actually supplied amount ofoxygen to the theoretical amount of oxygen necessary for combustion.

6. A pyrometallurgical refining process for copper, wherein a moltenbath of unrefined copper is subjected to consecutive stages of heating,oxidation and reduction, said process comprising the steps of blowingdirectly into the bath of unrefined copper a mixture of air and a fuelselected from the group consisting of liquid oil and solid carbonaceousmaterial while heating the bath, the density of oxygen in the air beingadjusted in accordance with the type of fuel, further adjusting thevolume of oxygen in the air to a mixture ratio capable of oxidizing thecopper, continuing the blowing of the adjusted mixture directly'into thecopper bath until the oxidation is completed, further adjusting thevolume of oxygen in the air to a mixture ratio capable of reducing thecopper, and then continuing the blowing of the adjusted mixture directlyinto the copper bath until the reduction is completed,

7. A pyrometallurgical refining process for copper, wherein a moltenbath of unrefined copper is subjected to consecutive stages of heating,oxidation and reduction, said process comprising the steps of blowingdirectly into the bath of unrefined copper a mixture of oxygen and afuel selected from the group consisting of liquid oil and solidcarbonaceous material while heating the bath, adjusting the volume ofoxygen in the mixture to an oxygen-fuel ratio capable of oxidizing thecopper, continuing the blowing of the adjusted mixture directly into thecopper bath while violently stirring the bath until the oxidation iscompleted, whereby impurities are effectivelyseparated' and eliminatedfrom the copper, adjusting the volume of oxygen in the mixture to anoxygenfuel ratio capable of reducing the copper, and then continuing theblowing of the adjusted mixture directly into the copper bath until thereduction is completed.-

8. A pyrometallurgical refining process for copper, wherein a moltenbath of unrefined copper is subjected to consecutive stages of heating,oxidation and reduction, said process comprising the steps ofblowing-directly into the bath of unrefined copper a mixture of oxygenand a fuel selected from the group consisting Of liquid oil and solidcarbonaceous material while heating the bath, adjusting the volume ofoxygen in the mixture to an oxygen-fuel ratio capable of oxidizing thecopper, continuing the blowing of the adjusted rnixture directly intothe copper bath until the oxidation is completed, adjusting the volumeof oxygen in the mixture to an oxygen-fuel ratio capable of reducing thecopper, and then continuing the blowing of the adjusted mixture directlyinto the copper bath while stirring the bath until the reduction iscompleted.

References Cited by the Examiner DAVID L. RECK, Primary Examiner.

BENIAMIN' HENKIN, Examiner.

H. W. CUMMINGS, C. N. LOVELL,

Assistant Examiners.

1. A PYROMETALLURGICAL REFINING PROCESS FOR COPPER WHEREIN A MOLTEN BATHOF UNREFINED COPPER IS SUBJECTED TO CONSECUTIVE STAGES OF HEATING,OXIDATION AND REDUCTION, SAID PROCESS COMPRISING THE STEPS OF BLOWINGDIRECTLY INTO THE BATH OF UNREFINED COPPER A MIXTURE OF OXYGEN AND AFUEL SELECTED FROM THE GROUP CONSISTING OF LIQUID OIL AND SOLIDCARBONACEOUS MATERIAL WHILE HEATING THE BATH, ADJUSTING THE VOLUME OFOXYGEN IN THE MIXTURE TO AN OXYGEN-FUEL RATIO CAPABLE OF OXIDIZING THECOPPER, CONTINUING THE BLOWING OF THE ADJUSTED MIXTURE DIRECTLY INTO THECOPPER BATH UNTIL THE OXIDATION IS COMPLETED, ADJUSTING THE VOLUME OFOXYGEN IN THE MIXTURE TO AN OXYGEN-FUEL RATIO CAPABLE OF REDUCING THECOPPER, AND THEN CONTINUING THE BLOWING OF THE ADJUSTED MIXTURE DIRECTLYINTO THE COPPER BATH UNTIL THE REDUCTION IS COMPLETED.